This invention generally relates to downhole well jar apparatus as utilized in the drilling and related operations for oil and gas wells. More specifically, the invention pertains to an advance in well jars of the mechanical type as exemplified by the tools disclosed in the prior art.
Well jar apparatus is generally provided of the mechanical type as herein disclosed and of the hydraulic type as well.
The principal disadvantage of the hydraulic type well jars is that they become overheated with continuouo use and become either ineffective or inoperative due to the heat. On the other hand, most of the mechanical type jars are difficult to adjust, if adjustable, to provide a designated jar impact force. Also, when the impact force of the jar can be adjusted, the jar must be adjusted at the earth's surface for any readjustment. Also, the latching or triggering mechanisms in mechanical jars, such as spherical balls for example are subject to very rigorous wear and deformation forces. Such forces limit the useful term of these mechanical jars between their rebuild or replacement.
The presently known prior art are the following: Beck No. 1989,906, Phipps No. 2,122,751, Kennedy et al No. 2,166,299, Howard No. 2,634,102, Andrews No. 2,882,018, Anderson No. 3,880,249, and Taylor No. 4,333,542.